The dand fblock elements - Result Question 23
####23. In which of the following pairs are both the ions coloured in aqueous solutions ?
[2006]
(a) $Sc^{3+}, Ti^{3+}$
(b) $Sc^{3+}, Co^{2+}$
(c) $Ni^{2+}, Cu^{+}$
(d) $Ni^{2+}, Ti^{3+}$
(At. no. : $Sc=21, Ti=22, Ni=28, Cu=29, Co=27$ )
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Solution:
- (d) $Sc^{3+}: 1 s^{2}, 2 s^{2} p^{6}, 3 s^{2} p^{6} d^{0}, 4 s^{0}$; no unpaired electron.
$Cu^{+}: 1 s^{2}, 2 s^{2} p^{6}, 3 s^{2} p^{6} d^{10}, 4 s^{0}$; no unpaired electron.
$Ni^{2+}: 1 s^{2}, 2 s^{2} p^{6}, 3 s^{2} p^{6} d^{8}, 4 s^{0} ; 2$ unpaired electron present.
$Ti^{3+}: 1 s^{2}, 2 s^{2} p^{6}, 2 s^{2} p^{6} d^{1}, 4 s^{0} ; 1$ unpaired electron present
$Co^{2+}: 1 s^{2}, 2 s^{2} p^{6}, 3 s^{2} p^{6} d^{7}, 4 s^{0} ; 3$ unpaired electron present
So, from the given option, the only correct combination is $Ni^{2+}$ and $Ti^{3+}$
